Re: [fuse-devel] [PATCH] fuse: don't invalidate attrs to clear atime when not using atime

[Miklos S. <mi...@sz...>]

On Tue, Nov 05, 2013 at 03:55:43AM -0800, Andrew Gallagher wrote:
> From: Andrew Gallagher <and...@fb...>
> 
> Various read operations (e.g. readlink, readdir) invalidate the
> cached attrs for atime changes.  However, mounts that have disabled
> atime can avoid this invalidation and any performance cose.  This
> patch adds a new function 'fuse_invalidate_atime' modeled around
> the 'touch_atime' function that which performs the various checks
> for noatime situations and avoids the attr invalidation in that case.

Doing it based on "MNT_NOATIME" isn't going to work, unfortunately: the
nameidata in ->follow_link() doesn't contain a valid path.  And besides, it's
ugly.  So lets just base this on MS_RDONLY, which implies NOATIME already.

Updated, untested patch follows.

Thanks,
Miklos


---
 fs/fuse/dir.c    |   14 ++++++++++++--
 fs/fuse/file.c   |    4 ++--
 fs/fuse/fuse_i.h |    2 ++
 3 files changed, 16 insertions(+), 4 deletions(-)

--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -112,6 +112,16 @@ void fuse_invalidate_attr(struct inode *
 	get_fuse_inode(inode)->i_time = 0;
 }
 
+/**
+ * Mark the attributes as stale due to an atime change.  Avoid the invalidate if
+ * atime is not used.
+ */
+void fuse_invalidate_atime(struct inode *inode)
+{
+	if (!IS_RDONLY(inode))
+		fuse_invalidate_attr(inode);
+}
+
 /*
  * Just mark the entry as stale, so that a next attempt to look it up
  * will result in a new lookup call to userspace
@@ -1371,7 +1381,7 @@ static int fuse_readdir(struct file *fil
 	}
 
 	__free_page(page);
-	fuse_invalidate_attr(inode); /* atime changed */
+	fuse_invalidate_atime(inode);
 	return err;
 }
 
@@ -1404,7 +1414,7 @@ static char *read_link(struct dentry *de
 		link[req->out.args[0].size] = '\0';
  out:
 	fuse_put_request(fc, req);
-	fuse_invalidate_attr(inode); /* atime changed */
+	fuse_invalidate_atime(inode);
 	return link;
 }
 
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -687,7 +687,7 @@ static int fuse_readpage(struct file *fi
 		SetPageUptodate(page);
 	}
 
-	fuse_invalidate_attr(inode); /* atime changed */
+	fuse_invalidate_atime(inode);
  out:
 	unlock_page(page);
 	return err;
@@ -716,7 +716,7 @@ static void fuse_readpages_end(struct fu
 			fuse_read_update_size(inode, pos,
 					      req->misc.read.attr_ver);
 		}
-		fuse_invalidate_attr(inode); /* atime changed */
+		fuse_invalidate_atime(inode);
 	}
 
 	for (i = 0; i < req->num_pages; i++) {
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -788,6 +788,8 @@ void fuse_invalidate_attr(struct inode *
 
 void fuse_invalidate_entry_cache(struct dentry *entry);
 
+void fuse_invalidate_atime(struct inode *inode);
+
 /**
  * Acquire reference to fuse_conn
  */